Djikstra with Cost Cypher Implementation?

[Ben Campbell]

Anyone know when the Djikstra/A* with cost implementation is being implemented in cypher? It appears to have been accessible from the Web API for a long time, but no easy way to use it when using bolt? 

Is there a reliable workaround? I basically want to call shortestPath but specify a cost parameter stored on each relationship. I've seen workarounds on stackoverflow, but these appear to work after obtaining all the results so become inefficient? 

[Michael Hunger]

Hi Ben,

it is exposed as user defined procedure in the apoc library.

You can find it here: https://neo4j-contrib.github.io/neo4j-apoc-procedures/#_graph_algorithms_work_in_progress

Install Instructions (just download and drop the jar into NEO4J_HOME/plugins) are in the readme: 

https://neo4j-contrib.github.io/neo4j-apoc-procedures/#_download_latest_release_for_the_regular_user

apoc.algo.dijkstra(startNode, endNode, 'KNOWS|<WORKS_WITH|IS_MANAGER_OF>', 'distance') YIELD path, weight	run dijkstra with relationship property name as cost function
apoc.algo.dijkstraWithDefaultWeight(startNode, endNode, 'KNOWS|<WORKS_WITH|IS_MANAGER_OF>', 'distance', 10) YIELD path, weight	run dijkstra with relationship property name as cost function and a default weight if the property does not exist

In Neo4j 3.0+ shortest path functions pull in predicates into the evaluation, so something like

 WHERE reduce(sum = 0 , x in rels(path) |  sum + x.weight )  < 100 

should work

On Fri, Sep 16, 2016 at 12:47 PM, Ben Campbell <campb...@hotmail.com> wrote:

Anyone know when the Djikstra/A* with cost implementation is being implemented in cypher? It appears to have been accessible from the Web API for a long time, but no easy way to use it when using bolt? 

Is there a reliable workaround? I basically want to call shortestPath but specify a cost parameter stored on each relationship. I've seen workarounds on stackoverflow, but these appear to work after obtaining all the results so become inefficient? 

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[Ben Campbell]

Hi Michael,

This looks just the ticket. Having a look through the documentation it seems to solve a lot of my Neo4j Cypher woes, wish I had heard of it earlier.

Cheers,

Ben

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[Michael Hunger]

Glad it helped :)

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